Micro-electro-mechanical valves and pumps and methods of fabricating same

ABSTRACT

Micro-valves and micro-pumps and methods of fabricating micro-valves and micro-pumps. The micro-valves and micro-pumps include electrically conductive diaphragms fabricated from electrically conductive nano-fibers. Fluid flow through the micro-valves and pumping action of the micro-pumps is accomplished by applying electrostatic forces to the electrically conductive diaphragms.

This application is a continuation of U.S. patent application Ser. No.11/276,772 filed on Mar. 14, 2006.

FIELD OF THE INVENTION

The present invention relates to the field of micro-electro-mechanicalvalves and pumps; more specifically, it relates tomicro-electro-mechanical valves and pumps having carbon nanotubediaphragms and methods of fabricating micro-electro-mechanical valvesand pumps having conductive nano-fiber diaphragms.

BACKGROUND OF THE INVENTION

In recent years, a need has developed for micro-fluidic devices capableof delivering extremely small quantities of fluids very precisely.Examples of potential uses of such devices include micro-fuel cells,micro-chemical analysis and delivery of micro-doses of medications.Therefore, there is an ongoing need for micro-electro-mechanical valvesand pumps.

SUMMARY OF THE INVENTION

A first aspect of the present invention is a micro-valve having an inletand an outlet, the micro-valve comprising: a lower chamber having abottom wall and sidewalls and an upper chamber having a top wall andsidewalls, a bottom of the upper chamber separated from a top of thelower chamber by a porous, flexible and electrically conductive mat ofnano-fibers; an opening in the top wall of the upper chamber; animpervious valve seal on the mat of nano-fibers, the valve seal belowand self-aligned to the first opening; an electrically conductive plateunder the bottom wall of the lower chamber; a first electrical contactto the conductive plate; and a second electrical contact to the mat ofnano-fibers.

A second aspect of the present invention is the first aspect wherein theoutlet is comprised of the opening in the top wall of the upper chamberand the inlet is comprised of an additional opening in the top wall ofthe upper chamber.

A third aspect of the present invention is the second aspect, whereinthe micro-valve is a normally-open valve.

A fourth aspect of the present invention is the first aspect, furtherincluding: a valve seat defined by an edge of the opening along aninterior surface of the upper wall of the upper chamber.

A fifth aspect of the present invention is the first aspect, furtherincluding a valve seat formed on sidewalls of the opening.

A sixth aspect of the present invention is the first aspect, wherein aregion of the top wall of the upper chamber adjacent to the opening isthicker than a region of the top wall of the upper chamber away from theopening.

A seventh aspect of the present invention is the sixth aspect, whereinthe outlet is comprised of the opening in the top wall of the upperchamber and the inlet is comprised of an additional opening in the topwall of the upper chamber.

An eighth aspect of the present invention is the seventh aspect, whereinthe micro-valve is a normally-closed valve.

A ninth aspect of the present invention is the sixth aspect, furtherincluding: a valve seat defined by an edge of the opening along aninterior surface of the upper wall of the upper chamber.

A tenth aspect of the present invention is the first aspect, furtherincluding: an additional conductive plate on top of the upper chamber; athird electrical contact to the additional conductive plate; and anadditional opening into the bottom chamber, the inlet comprised of theadditional opening and the outlet comprised of the opening.

A eleventh aspect of the present invention is the tenth aspect, whereinthe micro-valve is a normally-open valve.

A twelfth aspect of the present invention is the first aspect, furtherincluding a protective coating on nano-fibers of the mat of nano-fibers.

A thirteen aspect of the present invention is the first aspect, whereinthe valve seal is pushed against or pulled away from the opening inresponse to electrostatic forces applied to the mat of nano-fibers.

A fourteenth aspect of the present invention is the first aspect,wherein the micro-fibers are silicon filaments or carbon nanotubes.

BRIEF DESCRIPTION OF DRAWINGS

The features of the invention are set forth in the appended claims. Theinvention itself, however, will be best understood by reference to thefollowing detailed description of an illustrative embodiment when readin conjunction with the accompanying drawings, wherein:

FIGS. 1A through 1N are cross-sectional drawings illustratingfabrication of a normally-open valve and a normally-closed micro-valveaccording to a first embodiment of the present invention;

FIGS. 1O and 1P are cross-sectional drawings illustrating operation ofthe normally-closed micro-valve according to the first embodiment of thepresent invention;

FIGS. 2A through 2E are cross-sectional drawings illustratingfabrication of the normally-open micro-valve according to a secondembodiment of the present invention;

FIGS. 2F and 2G are cross-sectional drawings illustrating operation ofthe normally-open micro-valve according to a second embodiment of thepresent invention;

FIGS. 3A through 3G 2G are cross-sectional drawings illustratingfabrication of a micro-pump according to a third embodiment of thepresent invention;

FIG. 4 is a top view of the valve and pump chambers of the micro-pumpaccording to the third embodiment of the present invention;

FIGS. 5A through 5D are schematic drawings illustrating operation of themicro-pump according to the third embodiment of the present invention;

FIG. 6 is a top view of the valve and pump chambers of a micro-pumpaccording to a fourth embodiment of the present invention;

FIG. 7 is a top view of the valve and pump chambers of a micro-pumpaccording to a fifth embodiment of the present invention; and

FIGS. 8A through 8C are schematic drawings illustrating operation of themicro-pump according to the fourth embodiment of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

The term normally-open when applied to an electrostatically operatedvalve as described herein is defined a valve that allows fluid to flowfrom an inlet of the valve to an outlet of the valve when no power orvoltage potentials are applied to the valve.

The term normally-closed when applied to an electrostatically operatedvalve as described herein is defined a valve that blocks fluid fromflowing from an inlet of the valve to an outlet of the valve when nopower or voltage potentials are applied to the valve.

The terms impervious and non-porous may be used interchangeably and arerelative to either the fluid being controlled by a micro-pump or pumpedby a micro-pump. The terms pervious and porous may be usedinterchangeably relative to either the fluid being controlled by amicro-pump or pumped by a micro-pump. The terms insulating anddielectric may be used interchangeably.

The term nano-fiber is defined as a thread, filament or tube having adiameter or cross-sectional area in a direction perpendicular to alongitudinal axis of the thread, fiber or tube no of less than onemicron. Examples of nano-fibers includes but are not limited to siliconfilaments and carbon nanotubes (CNTs). The nano-fibers of embodiments ofthe present invention are electrically conductive.

The embodiments of the present invention will be illustrated using CNTsand CNT mats. It should be remembered that other types ofconductive-nano-fibers and mats may be substituted for CNTs and CNTmats. The nano-fiber mats described herein may be considered diaphragms.

FIGS. 1A through 1N are cross-sectional drawings illustratingfabrication of a normally-open valve (FIGS. 1A through 1M) and anormally-closed micro-valve (FIGS. 1A through 1N) according to a firstembodiment of the present invention. In FIG. 1A, formed on a substrate100 is an insulating layer 105. Formed on insulating layer 105 is anelectrically conductive layer 110. Formed on conductive layer 110 is aninsulating layer 115. In one example, substrate 100 comprises silicon orquartz. In one example, insulating layers 105 and 115 independentlycomprise silicon dioxide, silicon nitride, quartz or polyimide. In oneexample, conductive layer 110 comprises copper, aluminum,aluminum-copper alloy, tungsten, tantalum, titanium, titanium nitride,tantalum nitride or combinations thereof.

In FIG. 1B, an insulating layer 120 is formed on insulating layer 115and a trench 125 is formed in insulating layer 120, exposing a topsurface 130 of insulating layer 115 in the bottom of the trench. In oneexample, insulating layer 120 comprises silicon dioxide, siliconnitride, quartz or polyimide. In one example, trench 125 may be formedby a photolithographic process to create a mask followed by a reactiveion etch (RIE) to remove unwanted portions of insulating layer 120 notprotected by the mask followed by removal of the mask.

In FIG. 1C, trench 125 is over-filled with a sacrificial material and achemical-mechanical-polish (CMP) performed so that a top surface of asacrificial fill 135 and a top surface of insulating layer 120 arecoplanar. Then a flexible carbon nanotube (CNT) mat 140 formed oversacrificial fill 135. CNT mat 140 overlaps onto insulating layer 120. Inone example, sacrificial fill 135 comprises germanium formed by lowpressure chemical vapor deposition (LPCVD) or plasma enhanced chemicalvapor deposition (PECVD). CNT mat 140 is comprised of layers of CNTs andis porous. In one example, CNT mat 140 is formed by spin application ofa suspension of CNTs in a volatile liquid. CNT mat 140 may comprisemultiple layers of CNT mats. CNT mat materials may be fabricated by anynumber of methods known in the art or may be purchased commercially. Onemethod of CNT preparation is described in United States PatentPublication US 2002/0090330 to Smalley et al., filed on Dec. 28, 2001,which is hereby incorporated by reference in its entity.

In FIG. 1D, sacrificial fill 135 (see FIG. 1C) is removed to create achamber 145. If sacrificial fill 135 is germanium, the sacrificial fillmay be removed by etching with a solution of hydrogen peroxide. Next, anoptional protective coating is applied to CNT mat 140 (see FIG. 1C) toproduce a flexible coated CNT mat 155. Suitable coating materialsinclude dielectrics, metals and polymers that may be applied, forexample, by sputter deposition, PECVD or atomic layer deposition (ALD).In one example, the coating material is silicon nitride applied to forma 50 Å thick layer over individual CNTs. Coated CNT mat 155 is porous,the coating material not filling all the voids in the mat. A thin layer150 of coating material may be formed on the bottom and sidewalls ofchamber 145.

In FIG. 1E, an insulating layer 160 is formed on coated CNT mat 155, atrench is formed in insulating layer 160 and over-filled with asacrificial fill 165. A chemical-mechanical-polish (CMP) performed sothat a top surface of sacrificial fill 165 and a top surface ofinsulating layer 160 are coplanar. In one example, insulating layer 160comprises silicon dioxide, silicon nitride, quartz or polyimide. In oneexample, sacrificial fill 165 comprises germanium formed by low pressurechemical vapor deposition (LPCVD) or plasma enhanced chemical vapordeposition (PECVD).

In FIG. 1F, a first dielectric layer 170 is formed on insulating layer160 and sacrificial fill 165. Next, an electrically conductive layer 175is formed on first dielectric layer 170. Then a second dielectric layer180 is formed on conductive layer 175. In one example, first and seconddielectric layers 170 and 180 are silicon nitride and conductive layer175 is polysilicon.

In FIG. 1G, trenches 185, 190 and 195 are formed. Trench 185 extendsthough second dielectric layer 180, conductive layer 175, firstdielectric layer 170 and insulating layer 160. Coated CNT mat 155 isexposed in the bottom of trench 185. Trench 190 extends though seconddielectric layer 180, conductive layer 175 and first dielectric layer170. Sacrificial fill 165 is exposed in the bottom of trench 190. Trench195 extends though second dielectric layer 180, conductive layer 175,first dielectric layer 170, insulating layer 160, coated CNT mat 155,insulating layer 120 and insulating layer 115. Conductive layer 110 isexposed in the bottom of trench 195. In one example, trenches 185 and190 are formed and protected (for example by a layer of photoresist) andtrench 195 then formed. In one example, trenches 185, and 190 and aportion of trench 195 to coated CNT mat 155 are formed and protected(for example by a layer of photoresist) and the remainder of trench 195is formed. Formation of trenches 185, 190 and 195 may be accomplished byphotolithographic processes followed by RIE and removal of photoresistlayers. Silicon nitride and silicon dioxide may be etched using afluorine-based RIE. CNTs may be etched using an oxygen-based RIE (afterremoval of the silicon nitride coating).

In FIG. 1H, silicon nitride spacers 200 are formed on the sidewalls oftrench 185, silicon nitride spacers 205 are formed on the sidewalls oftrench 190 and silicon nitride spacers 210 are formed on the sidewallsof trench 195. Spacers are formed by deposition of a conformal layerfollowed by RIE to remove the conformal coating from horizontal surfaces(e.g. second dielectric layer 180 and the bottoms of trenches 185, 190and 195) while leaving the conformal coating on vertical surfaces (e.g.the sidewalls of trenches 185, 190 and 195). The spacer RIE process (oranother RIE process) removes the coating from coated CNT mat 155,leaving carbon nanotubes 220 exposed in the bottom of trench 185. If thecoating of coated CNT mat 155 is electrically conductive (for example, ametal) then the coating need not be removed.

In FIG. 1I, a damascene process is performed to form electricallyconductive contacts 215, 225 and 230. Contact 215 electrically contactscoated CNT mat 155 through exposed carbon nanotubes 220, contact 225electrically contacts sacrificial fill 165 and contact 230 electricallycontacts conductive layer 110. A damascene process is one in whichtrenches are formed in a dielectric layer, an electrical conductor ofsufficient thickness to fill the trenches is deposited on a top surfaceof the dielectric, and a chemical-mechanical-polish (CMP) process isperformed to remove excess conductor and make the surface of theconductor co-planer with the surface of the dielectric layer to form adamascene contact (or via or wire). In one example, contacts 215, 225and 230 each comprise copper, aluminum, aluminum-copper alloy, tungsten,tantalum, titanium, titanium nitride, tantalum nitride or combinationsthereof.

In FIG. 1J, contact 225 (see FIG. 1I) is removed and a thin conformalsilicon nitride layer 235 formed. Silicon nitride layer 235 covers andprotects sacrificial fill 165 in the bottom of an opening 190A.

In FIG. 1K, an opening 240 is formed over sacrificial fill 165. Opening240 extends though second dielectric layer 180, conductive layer 175 andfirst dielectric layer 170. Sacrificial fill 165 is exposed in thebottom of trench 190A.

In FIG. 1L, sacrificial fill 165 (see FIG. 1K) is removed to form achamber 245 over chamber 145. Chamber 145 and 245 are separated byporous coated CNT mat 155. If sacrificial fill 165 (see FIG. 1K) isgermanium, the sacrificial fill may be removed by etching with asolution of hydrogen peroxide

In FIG. IM, an impervious valve seat 245 and impervious valve seal 250are simultaneously formed on the sidewalls of opening 240 and on aportion of coated CNT mat 155 directly under opening 240. Since valveseal 250 is formed through opening 240, valve seal 250 is self-alignedto opening 240 and valve seat 245. Suitable materials for valve seat 245and valve seal 250 include dielectric, metal and polymers that may beapplied, for example, by sputter deposition or PECVD using mask (asillustrated) which is then removed. By removal of silicon nitride layer235 in opening 190A, a fully functional normally-open (NO) valve may beobtained.

It should be appreciated that if a NO valve is desired, only firstdielectric layer 170 is required and conductive layer 175 and seconddielectric layer 180 may be eliminated. Alternatively, first dielectriclayer 170, conductive layer 175 and second dielectric layer 180 may bereplaced by a layer of dielectric material.

For a normally-closed (NC) valve, the valve seat 245 and valve seal 250material needs to withstand the about 700° C. to about 800° C.temperature of the process described infra in reference to FIG. 1Nwithout adverse effects.

In FIG. 1N, a thermal oxidation (in one example in steam or oxygenbetween about 700° C. and about 800° C.) is performed to oxidize regionsof conductive layer 175 adjacent to opening 240 (see FIG. 1M) to formsilicon oxide regions 255 and an outlet 256. The protective coatingapplied to coated CNT mat 155 protects the CNTs of the coated CNT matfrom being oxidized by the thermal oxidation. Because there is about a40% to about a 60% increase in volume when silicon is oxidized, seconddielectric layer 180 is forced upward and first dielectric layer 170 isforced downward to contact valve seal 250. Removal of silicon nitridelayer 235 (see FIG. 1M) forms an inlet 190B and completes fabrication ofa NC valve according to the first embodiment of the present invention.

FIGS. 1O and 1P are cross-sectional drawings illustrating operation ofthe normally-closed micro-valve according to the first embodiment of thepresent invention. In FIG. 1O, a NC valve 257 is shown in the closedposition. There is no fluid transfer between inlet 190B and outlet 256.In FIG. 1P, with no voltage potentials (or the same polarity voltagepotential) applied to contacts 215 and 230 valve seal 250 is pressedagainst the edge 258 of silicon-nitride layer 170 along the periphery ofoutlet 240A due to the normal resiliency of coated CNT mat 155. Edge 258is the valve seat of NC valve 257. Because coated CNT mat 155 is porous,fluid from chamber 245 can pass into chamber 145 and fluid in chamber145 can pass into chamber 245. The pressure of the fluid on the inletside of valve 257 helps to keep valve seal 250 pressed against valveseat 258. Because the pressure in chambers 145 and 245 is the same,little force is required to open valve 257.

In FIG. 1P, opposite voltage potentials are applied across contacts 215and 230. For example, with a negative voltage potential on contact 215,coated CNT mat 255 charges negatively and with a positive voltagepotential applied to contact 230, conductive layer 110 charge positivelythus electrostatically attracting coated CNT mat 155 toward theconductive layer, away from valve seat 258, opening valve 257.

The operation of the NO valve illustrated supra in reference to FIG. 1Moperates in a similar manner except it is open with no voltagepotentials applied top contacts 215 and 230 and closed when the samevoltage potential polarity is applied to the contacts. Alternatively, amore positive valve actuation may be provided by forming an electricalconnection 262 to conductive layer 175 and applying a voltage potentialto conductive layer 175 opposite to that applied to contact 215.

FIGS. 2A through 2E are cross-sectional drawings illustratingfabrication of the normally-open micro-valve according to a secondembodiment of the present invention. FIG. 2A is similar to FIG. 1Cexcept an insulating layer 265 is formed on CNT mat 140, a trench isformed in insulating layer 265 and over-filled with a sacrificialmaterial, a CMP performed so that a top surface of a sacrificial fill270 and a top surface of insulating layer 265 are coplanar, aninsulating layer 275 is formed on top of insulating layer 265 andsacrificial fill 270, an electrically conductive layer 280 is formed oninsulating layer 275 and an insulating layer 285 is formed on conductivelayer 280. In one example, insulating layers 265, 275 and 285independently comprise silicon dioxide, silicon nitride, quartz orpolyimide. In one example, sacrificial fill 270 is germanium formed byLPCVD or PECVD. In one example, conductive layer 280 comprises copper,aluminum, aluminum-copper alloy, tungsten, tantalum, titanium, titaniumnitride, tantalum nitride or combinations thereof.

In FIG. 2B, trenches 290 and 295 are formed. Trench 290 extends thoughinsulating layer 285, conductive layer 280, insulating layer 275 andinsulating layer 265. CNT mat 140 is exposed in the bottom of trench290. Trench 295 extends though insulating layer 285, conductive layer280, insulating layer 275, insulating layer 265 and, mat 140, insulatinglayer 120 and insulating layer 115. Conductive layer 110 is exposed inthe bottom of trench 195. In one example, trench 290 is formed andprotected (for example by a layer of photoresist) and trench 295 thenformed. In one example, trench 290 and a portion of trench 295 down toCNT mat 140 is formed and protected (for example by a layer ofphotoresist) and the remainder of trench 295 is formed. Formation oftrenches 290 and 295 may be accomplished by photolithographic processesfollowed by RIE and removal of photoresist layers.

Additionally, spacers 300 are formed on the sidewalls of trench 290 andspacers 305 are formed (as described supra) on sidewalls of trench 285.In one example, spacers 300 and 305 comprise silicon nitride.

In FIG. 2C, a trench 310 is formed in insulating layer 285, exposingconductive layer 280 in the bottom of trench 310. Then a damasceneprocess (as described supra) is performed to form electricallyconductive contacts 310, 315 and 320. Contact 310 electrically contactsconductive layer 280, contact 315 electrically contacts CNT mat 140 andcontact 320 electrically contacts conductive layer 110. In one example,contacts 310, 315 and 320 each comprise copper, aluminum,aluminum-copper alloy, tungsten, tantalum, titanium, titanium nitride,tantalum nitride or combinations thereof.

In FIG. 2D, trench 240 is formed through insulating layer 285,conductive layer 280 and insulating layer 275 to expose sacrificial fill270 (see FIG. 2C). Then sacrificial fill 270 and sacrificial fill 135(see FIG. 2C) are removed to form respective chambers 330 and 335separated by CNT mat 140. If sacrificial fill 135 and sacrificial fill270 are germanium, the sacrificial fills may be removed by etching witha solution of hydrogen peroxide.

In FIG. 2E, valve seat 245 and valve seal 250 are simultaneously formedon the sidewalls of opening 240 (see FIG. 2D) and on a portion of CNTmat 140 directly under opening 240 as described supra in reference toFIG. 1M. Since valve seal 250 is formed through opening 240, valve seal250 is self-aligned to opening 240 and to valve seat 245. Also, opening240 becomes outlet 332. Since CNT mat 140 is porous, a small quantity ofvalve seat/valve seal material 250A may deposit on the bottom of chamber335 under valve seal 250.

FIGS. 2F and 2G are cross-sectional drawings illustrating operation ofthe normally-open micro-valve according to a second embodiment of thepresent invention. In FIG. 2F, a NO valve 337 is shown in the closedposition. There is no fluid transfer between an inlet 338 and outlet332. A “generic” inlet is shown. Inlet 338 opens into chamber 335 andmay be formed to enter from a bottom of chamber 335, a sidewall ofchamber 335 or a top of chamber 335 if chamber 335 extends in a lateraldirection (parallel to a top surface of substrate 100) further thanchamber 330 extends in the lateral direction (i.e. when chamber 335 islonger or wider than chamber 330).

In FIG. 2F, with a negative voltage potential applied to contacts 315and 320 and a positive voltage potential applied to contact 325, CNT mat140 and conductive layer 110 charge negatively and conductive layer 280charges positively. This electrostatically attracts CNT mat 140 towardconductive layer 280 and electrostatically repels CNT mat 140 fromconductive layer 110, thus pressing valve seal 250 against edge 339 ofvalve seal 245 and closing valve 337. Because CNT mat 140 is porous,fluid from chamber 335 can pass into chamber 330 and fluid in chamber330 can pass into chamber 355. The pressure of the fluid on the inletside of NO valve 337 helps to keep valve seal 250 pressed against valveseat 245. Because the pressure in chambers 330 and 335 is the same,little force is required to close NO valve 337.

With no voltage potentials applied to contacts 315, 320 and 325, NOvalve 337 is open and CNT mat 140 remains unflexed (see FIG. 2E).However, by reversing the voltage potential polarities on contacts 320and 325 an enhanced open position of NO valve 337 may be obtained asillustrated in FIG. 2G.

In FIG. 2G, with a negative voltage potential applied to contacts 315and 325 and a positive voltage potential applied to contact 320, CNT mat140 and conductive layer 280 charge negatively and conductive layer 110charges positively. This electrostatically attracts CNT mat 140 towardconductive layer 110 and electrostatically repels CNT mat 140 fromconductive layer 280, thus pulling valve seal 250 away from edge 339 ofvalve seal 245 and enhancing the opening of NO valve 337. Because CNTmat 140 is porous, fluid from chamber 335 can pass into chamber 330 andfluid in chamber 330 can pass into chamber 355. Because the pressure inchambers 330 and 335 is the same, little force is required to open NOvalve 337.

FIGS. 3A through 3G are cross-sectional drawings illustratingfabrication of a micro-pump according to a third embodiment of thepresent invention. FIGS. 3A and 3B are similar to FIGS. 1B and 1C excepttwo trenches, trench 125A and 125B are formed in insulating layer 120and filled with sacrificial fill 135A and 135B respectively. Topsurfaces of sacrificial fill 135A and 135B and a top surface ofinsulating layer 120 are coplanar. In one example, sacrificial fills135A and 135B comprise germanium. Trench 125A will become a part of oneof two valves required for the micro-pump of the present invention andtrench 125B will form a part of a pump section of the micro-pump.Fabrication of only one valve is illustrated in FIGS. 3A through 3G,fabrication of the second valve is identical to fabrication of the firstvalve.

In FIG. 3C, CNT mat 140 (see FIG. 3B) is cut into electrically isolatedCNT mat 140A and CNT mat 140B, and sacrificial fills 135A and 135B (seeFIG. 3B) are removed to form respective chambers 145A and 145B. Ifsacrificial fills 13A and 135B are germanium, sacrificial fills 135A and135B may be removed by etching with a solution of hydrogen peroxide.

In FIG. 3D, a CNT mat 155A is porous and a CNT mat 155B is non-porous(e.g. impervious to the fluid that will be pumped or to a gas trapped inchamber 145B). In a first method, both CNT mat 140A and 140B (see FIG.3C) are coated with a thickness of material sufficient to seal the voidsbetween the CNTs and then all or a portion of the coating is removedfrom CNT mat 140A using, for example, an RIE process. In a secondmethod, only CNT mat 140B is coated by using a photolithographic maskingprocess. A thin layer 150A of coating material may be formed on thebottom and sidewalls of chamber 145A and a thin layer 150B of coatingmaterial may be formed on the bottom and sidewalls of chamber 145B.Suitable coating materials include dielectrics, metals and polymers thatmay be applied, for example, by sputter deposition, PECVD or ALD. In oneexample, the coating material is silicon nitride applied by PECVD orALD.

Since CNT mat 155B is sealed, a gas or partial vacuum may be trapped inchamber 145B.

FIG. 3E is similar to FIG. 1E except, a trench is formed in insulatinglayer 160 and filled with a sacrificial fill 350 and sacrificial fill350 extends over both chamber 145A and 145B (as well as a second valvechamber 145C not shown in FIG. 3E). A top surface of sacrificial fill350 and a top surface of insulating layer 160 are coplanar. A thin layer345 of fill material may be formed in chamber 145A.

In FIG. 3F, insulating layer 275 is formed on top of insulating layer160 and sacrificial fill 350, electrically conductive layer 280 isformed on insulating layer 275 and insulating layer 285 is formed onconductive layer 280. Insulating layers 275 and 285 and conductive layer280 have been described supra. A damascene contact 355 is formed toelectrically contact CNT mat 155A. A dielectric spacer 360 (in oneexample silicon nitride) electrically isolates contact 355 fromconductive layer 280. A damascene contact 365 is formed to electricallycontact CNT mat 155B. A dielectric spacer 370 (in one example siliconnitride) electrically isolates contact 365 from conductive layer 280. Adamascene contact 375 is formed to electrically contact conductive layer110. A dielectric spacer 380 (in one example silicon nitride)electrically isolates contact 375 from conductive layer 280 and CNT mat155B. A damascene contact 385 is formed to electrically contactconductive layer 280. In one example, contacts 355, 365, 375 and 385each comprise copper, aluminum, aluminum-copper alloy, tungsten,tantalum, titanium, titanium nitride, tantalum nitride or combinationsthereof.

In FIG. 3G, opening 240 is formed through insulating layer 285,conductive layer 280 and insulating layer 275 to expose sacrificial fill350 (see FIG. 3F) and then sacrificial fill material is removed to forma chamber 395. Opening 240 is formed over chamber 145A. If sacrificialfill 350 is germanium, the sacrificial fill may be removed by etchingwith a solution of hydrogen peroxide. Then valve seat 245 and valve seal250 are simultaneously formed on the sidewalls of opening 240 to form aninlet/outlet 397 and on a portion of CNT mat 155A directly under opening240 as described supra in reference to FIG. 1M. Since valve seal 250 isformed through opening 240, valve seal 250 is self-aligned to opening240 and valve seat 245.

In FIG. 3G, a micro-pump 400 includes a first valve 405A, a pump 405Band a second valve 405C (not shown) identical to first valve 405A andhaving a corresponding chamber 145C (not shown, see FIG. 4) and CNT mat155C (not shown) having a corresponding contact 350A (not shown). CNTmats 155A, 155B and 155C (not shown) are electrically isolated from eachother. First valve 405A comprises, opening 240, valve seat 245, valveseal 250, porous CNT mat 155A, chamber 145A and chamber 395. Pump 405Bcomprises a chamber 395, coated and non-porous CNT mat 155B and chamber145B. Second valve 405C (not shown) comprises, an opening 240C (notshown), a valve seat 245C (not shown), a valve seal 250C (not shown), aporous CNT mat 155C (not shown), a chamber 145C (not shown), and chamber395. First valve 405A may serve as an outlet of micro-pump 400 andsecond valve 405C (not shown) may serve as an inlet of micro-pump 400.

While NO valves have been shown in micro-pump 400 (see FIG. 3G) NCvalves as described supra, may be substituted.

FIG. 4 is a top view of the valve and pump chambers of the micro-pumpaccording to the third embodiment of the present invention. In FIG. 4,insulating layer 120 having chamber 145A of first valve 405A, chamber145B of pump 405B and chamber 145C of second valve 405C is illustrated.Line 3G-3G indicates the section through which FIG. 3G (as well as FIGS.3A through 3F were taken).

FIGS. 5A through 5D are schematic drawings illustrating operation of themicro-pump according to the third embodiment of the present invention.In FIG. 5A, chamber 145A is separated from chamber 395 by CNT mat 155A,chamber 145B is separated from chamber 395 by CNT mat 155B and chamber145C is separated from chamber 395 by CNT mat 155C. Chamber 395 includesan outlet 397A aligned over CNT mat 155A and an inlet 397C aligned overCNT mat 155C. Valve seals and seats are not shown, but are present asdescribed supra and illustrated in FIG. 3G. Electrical connections toconductive layers 110, 280, CNT mats 155A, 155B and 155C are also shown.In FIG. 5A no voltage potentials are applied to any of the electricalconnections.

In FIG. 5B, negative potential voltages are applied to conductive layer280, CNT mats 155B and 155C, and positive voltage potentials are appliedto conductive layer 110 and CNT mat 155A. CNT mat 155A iselectrostatically attracted to conductive layer 280 andelectrostatically repelled from conductive layer 110, closing outlet397A. CNT mats 155B and 155C electrostatically attracted to conductivelayer 110 and electrostatically repelled from conductive layer 280,further opening inlet 397C and pulling the fluid to be pumped intochamber 395.

In FIG. 5C, negative potential voltages are applied to conductive layer280 and CNT mat 155B and positive voltage potentials are applied toconductive layer 110 and CNT mats 155A and 155C. CNT mat 155A remainselectrostatically attracted to conductive layer 280 andelectrostatically repelled from conductive layer 110, maintaining theclosure of outlet 397A. CNT mat 155C is electrostatically attracted toconductive layer 280 and electrostatically repelled from conductivelayer 110, closing inlet 397C. CNT mat 155B remains electrostaticallyattracted to conductive layer 110 and electrostatically repelled fromconductive layer 280 trapping the fluid to be pumped in chamber 395.

In FIG. 5D, negative potential voltages are applied to conductive layer280 and CNT mat 155A, and positive voltage potentials are applied toconductive layer 110 and CNT mats 155B and 155C. CNT mat 155C remainselectrostatically attracted to conductive layer 280 andelectrostatically repelled from conductive layer 110, maintaining theclosure of inlet 397C. CNT mat 155A is electrostatically attracted toconductive layer 110 and electrostatically repelled from conductivelayer 280, opening outlet 397A. CNT mat 155B is electrostaticallyattracted to conductive layer 280 and electrostatically repelled fromconductive layer 110, thereby compressing the fluid to be pumped inchamber 395 and expelling fluid from chamber 395 through outlet 397A.

The sequence of voltage potential applications shown in FIGS. 5B through5D is repeated as the micro-pump operates. Enhanced operation of themicro-pump my be accomplished by splitting conductive layers 110 intothree section and 280 into three sections, each pair of sections alignedto one of chambers 145A, 145B and 145C and timing the application ofvoltage potentials to each of the three pairs of sections.

FIG. 6 is a top view of the valve and pump chambers of a micro-pumpaccording to a fourth embodiment of the present invention. In the fourthembodiment of the present invention two pumps according to the thirdembodiment of the present invention are arranged in parallel. In FIG. 6,formed in insulating layer 120 is a chamber 145A1 of a first valve, achamber 145C1 of a second valve, a first pump chamber 145B1, a chamber145A2 of a third valve, a chamber 145C2 of a fourth valve and a secondpump chamber 145B2. An opening 410 between first and second pumpchambers 145B1 and 145B2 allow the gas trapped in the first and secondpump chambers to freely pass between the pump chambers. Individual CNTsmats (not shown), each electrically isolated from each other andconnected to a different contact (not shown) separate chambers 145A1145B1 and 145C1 from a first common chamber (not shown) formed overchambers 145A1 145B1 and 145C1 as described supra. Individual CNTs mats(not shown), each electrically isolated from each other and connected toa different contact (not shown) separate chambers 145A2, 145B2 and 145C2from a second common chamber (not shown) formed over chambers 145A2,145B2 and 145C2 as described supra. The first and second common chambersare not connected to each other and the fluid to be pumped cannot passbetween the two common chambers.

FIG. 7 is a top view of the valve and pump chambers of a micro-pumpaccording to a fifth embodiment of the present invention. FIG. 7 issimilar to FIG. 6, except third and fourth chambers 145A2 and 145C2 (seeFIG. 6) are not present and the CNT mat (not shown) over first pumpchamber 145B1 is electrically isolated and not connected to a voltagepotential source. This pump arrangement is suitable for pumpingconductive fluids as described infra.

While two pumps in parallel have been illustrated in FIGS. 6 and 7, itwill be appreciated that any number of pumps may be connected inparallel. Pumps according to the present invention may also be connectedin series by forming conduits in additional layers of materials formedabove the pumps and connecting the inlet of one pump to the outlet ofanother pump.

FIGS. 8A through 8C are schematic drawings illustrating operation of themicro-pump according to the fourth embodiment of the present invention.In FIG. 8A, pump chamber 145B1 is separated from common chamber 395A byCNT mat 155B1 (the first and second valve chambers are not illustrated,but “share” common chamber 395A and pump chamber 145B2 is separated fromcommon chamber 395B by CNT mat 155B2 (the third and fourth valvechambers are not illustrated, but “share” common chamber 395B.Electrical connections to conductive layers 110, 280 and CNT mats 155B1and 155B2 are also shown. Connections to the CNT mats of the four valvesare not shown. In FIG. 8A no voltage potentials are applied to any ofthe electrical connections.

In FIGS. 8B and 8C, only the operation of the pump CNT mats 155B1 and155B2 will be described. In FIG. 8B, negative potential voltage isapplied to conductive layer 280 and CNT mat 155B1 and positive voltagepotentials are applied to conductive layer 110 and CNT mat 155B2. CNTmat 155B1 is electrostatically attracted to conductive layer 110 andelectrostatically repelled from conductive layer 280 pulling the fluidbeing pumped into chamber 395A. CNT mat 155B2 is electrostaticallyrepelled from conductive layer 110 and electrostatically attracted toconductive layer 280 pushing the fluid being pumped out of chamber 395B.A portion of the gas trapped in chamber 145B1 is transferred fromchamber 145B1 to 145B2.

In FIG. 8C, negative potential voltage is applied to conductive layer280 and CNT mat 155B2 and positive voltage potentials are applied toconductive layer 110 and CNT mat 155B1. CNT mat 155B1 iselectrostatically attracted to conductive layer 280 andelectrostatically repelled from conductive layer 110 pushing the fluidbeing pumped out of chamber 395A. CNT mat 155B2 is electrostaticallyrepelled from conductive layer 280 and electrostatically attracted toconductive layer 110 pulling the fluid being pumped into of chamber395B. A portion of the gas trapped in chamber 145B2 is transferred fromchamber 145B2 to 145B1

The sequence of voltage potential applications shown in FIGS. 8B and 8Cis repeated as the pump operates. The transfer of gas between chambers145B1 and 145B2 smoothes the operation of the pump. Enhanced operationof the micro-pump my be accomplished by splitting conductive layers 110into two sections and 280 into two sections, each pair of sectionsaligned to one of chambers 145B1 and 145B2 and timing the application ofvoltage potentials to each of the two pairs of sections.

The operation of the pump illustrated in FIG. 7 (fifth embodiment) issimilar to that described for the pump of FIG. 6 (fourth embodiment)supra, except there is no electrical connection to CNT mat 155B1 andflexure of CNT mat 155B1 is caused by gas transfer between chambers145B1 and 145B2. Since no conductive fluid that could interfere with theelectrostatic flexing of CNT mat 155B2 is present in chambers 145B2 and395B, the fifth embodiment of the present invention may beadvantageously used to pump conductive fluids. However valves 397A and397C must be NC valves and chambers 145A and 145C must be connected by apassage to relive back-pressure. Also a voltage connection to layer 280is not required.

Thus, the various embodiments of the present invention providemicro-electro-mechanical valves and pumps and methods of fabricatingmicro-electro-mechanical valves and pumps.

The description of the embodiments of the present invention is givenabove for the understanding of the present invention. It will beunderstood that the invention is not limited to the particularembodiments described herein, but is capable of various modifications,rearrangements and substitutions as will now become apparent to thoseskilled in the art without departing from the scope of the invention.Therefore, it is intended that the following claims cover all suchmodifications and changes as fall within the true spirit and scope ofthe invention.

1. A micro-valve having an inlet and an outlet, said micro-valvecomprising: a lower chamber having a bottom wall and sidewalls and anupper chamber having a top wall and sidewalls, a bottom of said upperchamber separated from a top of said lower chamber by a porous, flexibleand electrically conductive mat of nano-fibers; an opening in said topwall of said upper chamber; an impervious valve seal on said mat ofnano-fibers, said valve seal below and self-aligned to said firstopening; an electrically conductive plate under said bottom wall of saidlower chamber; a first electrical contact to said conductive plate; anda second electrical contact to said mat of nano-fibers.
 2. Themicro-valve of claim 1, wherein said outlet comprises said opening insaid top wall of said upper chamber and said inlet comprises anadditional opening in said top wall of said upper chamber.
 3. Themicro-valve of claim 2, wherein said micro-valve is a normally-openvalve.
 4. The micro-valve of claim 1, further including: a valve seatdefined by an edge of said opening along an interior surface of said topwall of said upper chamber.
 5. The micro-valve of claim 1, furtherincluding a valve seat formed on sidewalls of said opening.
 6. Themicro-valve of claim 1, wherein a region of said top wall of said upperchamber adjacent to said opening is thicker than a region of said topwall of said upper chamber away from said opening.
 7. The micro-valve ofclaim 6, wherein said outlet comprises said opening in said top wall ofsaid upper chamber and said inlet comprises an additional opening insaid top wall of said upper chamber.
 8. The micro-valve of claim 7,wherein said micro-valve is a normally-closed valve.
 9. The micro-valveof claim 6, further including: a valve seat defined by an edge of saidopening along an interior surface of said top wall of said upperchamber.
 10. The micro-valve of claim 1, further including: anadditional conductive plate on top of said upper chamber; a thirdelectrical contact to said additional conductive plate; and anadditional opening into said bottom chamber, said inlet comprised ofsaid additional opening and said outlet comprised of said opening. 11.The micro-valve of claim 10, wherein said micro-valve is a normally-openvalve.
 12. The micro-valve of claim 1, further including” a protectivecoating on nano-fibers of said mat of nano-fibers.
 13. The micro-valveof claim 1, wherein said valve seal is pushed against or pulled awayfrom said opening in response to electrostatic forces applied to saidmat of nano-fibers.
 14. The micro-valve of claim 1, wherein saidmicro-fibers are silicon filaments or carbon nanotubes.
 15. A micro-pumphaving an inlet and an outlet, said micro-pump comprising: a first lowerchamber having a bottom wall and sidewalls, a second lower chamberhaving a bottom wall and sidewalls, a third lower chamber having abottom wall and sidewalls, and an upper chamber having a top wall andsidewalls, a first region of a bottom of said upper chamber separatedfrom a top of said first lower chamber by a porous, flexible andelectrically conductive first mat of nano-fibers, a second region ofsaid bottom of said upper chamber separated from a top of said secondlower chamber by a non-porous, flexible and electrically conductivesecond mat of nano-fibers, and a third region of said bottom of saidupper chamber separated from a top of said third lower chamber by aporous, flexible and electrically conductive third mat of nano-fibers; afirst opening in said top wall of said upper chamber aligned over saidfirst mat of nano-fibers; a second opening in said top wall of saidupper chamber aligned over said third mat of nano-fibers; an imperviousfirst valve seal on said first mat of nano-fibers, said first valve sealbelow and self-aligned to said first opening; an impervious second valveseal on said third mat of nano-fibers, said second valve seal below andself-aligned to said second opening; a first electrically conductiveplate above said top walls of said first, second and third upperchambers and a second electrically conductive plate under said bottomwall of said lower chamber; a first electrical contact to said first matof nano-fibers; a second electrical contact to said second mat ofnano-fibers; a third electrical contact to said third mat ofnano-fibers; a fourth electrical contact to said first conductive plate;and a fifth electrical contact to said second conductive plate.
 16. Themicro-pump of claim 15, wherein said inlet comprises said first openingin said top wall of said upper chamber and said outlet comprises saidsecond opening in said top wall of said upper chamber.
 17. Themicro-pump of claim 15, further including: a first valve seat defined byan edge of said first opening along an interior surface of said top wallof said upper chamber; and a second valve seat defined by an edge ofsaid second opening along said interior surface of said top wall of saidupper chamber.
 18. The micro-pump of claim 15, further including: afirst valve seat formed on sidewalls of said first opening and a secondvalve seat formed on sidewalls of said second opening.
 19. Themicro-pump of claim 15, wherein regions of said top wall of said upperchamber adjacent to said first and second openings are thicker thanregions of said top wall of said upper chamber away from said first andsecond openings.
 20. The micro-pump of claim 19, further including: afirst valve seat defined by an edge of said first opening along aninterior surface of said top wall of said upper chamber; and a secondvalve seat defined by an edge of said second opening along said interiorsurface of said top wall of said upper chamber.
 21. The micro-pump ofclaim 15, further including: a coating on said second mat ofnano-fibers, said coating filling voids between said nano-fibers of saidsecond mat of carbon nano-tubes.
 22. The micro-pump of claim 15, whereinsaid first and second seals are pushed against or pulled away fromrespective said first and second openings in response to electrostaticforces applied to said first and third mats of nano-fibers.
 23. Themicro-pump of claim 15, wherein said second mat of nano-fibers isdeflectable into and out of said upper chamber and into and out of saidsecond lower chamber in response to electrostatic forces applied to saidfirst and third mats of nano-fibers.
 24. The micro-pump of claim 15,wherein said micro-fibers are silicon filaments.
 25. The micro-pump ofclaim 15, wherein said micro-fibers are carbon nanotubes.
 26. A methodof fabricating a micro-valve having an inlet and an outlet, said methodcomprising: on a substrate, forming a lower chamber having a bottom walland sidewalls and forming an upper chamber having a top wall andsidewalls, a bottom of said upper chamber separated from a top of saidlower chamber by a porous, flexible and electrically conductive mat ofnano-fibers; forming an opening in said top wall of said upper chamber;forming an impervious valve seal on said mat of nano-fibers, said valveseat below and self-aligned to said opening; forming a firstelectrically conductive plate above said top wall of said upper chamberand a second electrically conductive plate under said bottom wall ofsaid lower chamber; forming a first electrical contact to said firstconductive plate; forming a second electrical contact to said secondconductive plate; and forming a third electrical contact to said mat ofnano-fibers.
 27. The method of claim 26, wherein said outlet comprisessaid opening in said top wall of said upper chamber and said inletcomprises an additional opening in said top wall of said upper chamber.28. The method of claim 26, wherein a valve seat defined is by an edgeof said opening along an interior surface of said top wall of said upperchamber.
 29. The method of claim 26, further including: forming a valveseat on sidewalls of said opening.
 30. The method of claim 26, wherein aregion of said top wall of said upper chamber adjacent to said openingis thicker than a region of said top wall of said upper chamber awayfrom said opening.
 31. The method of claim 26, further including:forming an additional conductive plate on top of said upper chamber;forming a third electrical contact to said additional conductive plate;and forming an additional opening into said bottom chamber, said inletcomprised of said additional opening and said outlet comprised of saidopening.
 32. The method of claim 35, wherein: said first conductiveplate is formed on a insulating layer formed on a substrate; formingsaid lower chamber includes forming a first trench in a first dielectriclayer formed on said first conductive plate, filling said first trenchwith a first sacrificial material and forming said porous mat ofnano-fibers over said first sacrificial material followed by removingsaid first sacrificial material; and forming said upper chamber includesforming a second trench in a second dielectric layer formed on said matof nano-fibers, filling said second trench with a second sacrificialmaterial, forming a third dielectric layer on said second dielectriclayer and said second sacrificial material, forming a second conductivelayer on said third dielectric, forming a fourth dielectric layer onsaid second conductive layer and forming an opening though said fourthdielectric layer, said second conductive layer and said third dielectriclayer to said second sacrificial material and removing said secondsacrificial material.
 33. The method of claim 26, further including:forming a protective coating on nano-fibers of said mat of nano-fibers.34. The method of claim 26, wherein said micro-fibers are siliconfilaments or carbon nanotubes.
 35. A method of fabricating a micro-pumphaving an inlet and an outlet, said method comprising: forming a firstlower chamber having a bottom wall and sidewalls, forming a second lowerchamber having a bottom wall and sidewalls, forming a third lowerchamber having a bottom wall and sidewalls and forming an upper chamberhaving a top wall and sidewalls, forming a porous, flexible andelectrically conductive first mat of nano-fibers, said first mat ofnano-fibers separating a first region of a bottom of said upper chamberfrom a top of said first lower chamber, forming a non-porous, flexibleand electrically conductive second mat of nano-fibers, said second matof nano-fibers separating a second region of said bottom of said upperchamber from a top of said second lower chamber and forming a porous,flexible and electrically conductive third mat of nano-fibers, saidthird mat of nano-fibers separating a third region of said bottom ofsaid upper chamber from a top of said third lower chamber; forming afirst opening in said top wall of said upper chamber aligned over saidfirst mat of nano-fibers; forming a second opening in said top wall ofsaid upper chamber aligned over said third mat of nano-fibers; formingan impervious first valve seal on said first mat of nano-fibers, saidfirst valve seal below and self-aligned to said first opening; formingan impervious second valve seal on said third mat of nano-fibers, saidsecond valve seal below and self-aligned to said second opening; forminga first electrically conductive plate above said top wall of said first,second and third upper chambers and a second electrically conductiveplate under said bottom wall of said lower chamber; forming a firstelectrical contact to said first mat of nano-fibers; forming a secondelectrical contact to said second mat of nano-fibers; forming a thirdelectrical contact to said third mat of nano-fibers; forming a fourthelectrical contact to said first conductive plate; and forming a fifthelectrical contact to said second conductive plate.
 36. The method ofclaim 35, wherein said inlet comprises said first opening in said topwall of said upper chamber and said outlet comprises said second openingin said top wall of said upper chamber.
 37. The method of claim 35,wherein, a first valve seat is defined by an edge of said first openingalong an interior surface of said top wall of said upper chamber and asecond valve seat is defined by an edge of said second opening alongsaid interior surface of said top wall of said upper chamber.
 38. Themethod of claim 35, further including: forming a first valve seat onsidewalls of said first opening and forming a second valve seat onsidewalls of said second opening.
 39. The method of claim 35: furtherincluding: increasing the thickness of regions of said top wall of saidupper chamber adjacent to said first and second opening.
 40. The methodof claim 35, further including: forming a coating on said second mat ofnano-fibers, said coating filling voids between nano-fibers of saidsecond mat of carbon nano-tubes.
 41. The method of claim 35, whereinsaid micro-fibers are silicon filaments or carbon nanotubes.